This application makes reference to, incorporates herein and claims all benefits accruing from our application earlier filed in the Korean Industrial Property Office Dec. 31, 1993 of our application entitled OUTSIDE IMPACT RESISTANT APPARATUS AND METHOD BY AXIAL CONTROL OF HARD DISK DRIVE, which application was assigned Ser. No. 31792/1993.
The present invention relates to an apparatus providing axial control and outside impact resistance for a hard disk drive (HDD), and more particularly to an impact resistant apparatus and a method of axial control of a hard disk drive for continuously maintaining a magnetic head at a constant flying height (CFH) over a disk in an unsteady state. The method controls an active element equipped on a head suspension to achieve stabilization of signals read and written on the disk.
Recent trends in hard disk drive technology have created incentives to produce disk drive devices that are more light-weight and have a higher storage capacity. Accordingly, the track pitch and bit cell of contemporary hard disks have become minute. As a result, technologies have been devised wherein servo-mechanisms are carefully controlled to enable high precision read and write operations. These technologies basically require that the magnetic head of an actuator be maintained at a constant flying height above a top side of the disk (typically, less than 0.8 micrometers).
It is essential that the head be maintained at this requisite flying height above the disk in order to stabilize the electrical signals generated during reading and writing operations. The stabilization of these signals during the reading and writing operations is attained when the servo-mechanism is controlled with high precision.
A conventional device for maintaining a constant flying height of the head is disclosed in U.S. Pat. No. 5,012,369 entitled Head Suspension Mechanism Of A Recording Apparatus With A Constant Flying Height issued to Owe et al. on Apr. 30, 1991. In this invention, a load is beam is engaged by a pressing member to control the flying height of the head. The force of the pressing member is adjusted by a screw to maintain a constant flying height. While this invention purports to control flying height of the head, it contains no provision for the problem associated with the head contacting the surface of the disk.
In U.S. Pat. No. 5,115,664 entitled Tunable Feedback Transducer For Transient Friction Measurement issued to Hegde et al. on May 26, 1992, another conventional system for maintaining a fixed distance between system members is disclosed. In Hegde et al. ""664, an output is taken from a servomechanism to provide a signal proportional to a force exerted on a movable system member due to friction. While this invention may possess merit in its own right, it suffers from a problem in that the magnetic head is not prevented from contacting the disk. Accordingly, this system risks data destruction due to this contact and we therefore believe that an improved device can be constructed.
Therefore, it is an object of the present invention to provide an improved hard disk drive and control method therefor.
It is another object to provide a method and apparatus which can ensure the stabilization of electrical signals during reading and writing operations by continuously maintaining a desired constant flying height of a head.
It is still another object to provide a method and apparatus which can ensure the stabilization of electrical signals during reading and writing operations in both steady and unsteady operational states of a hard disk drive.
It is yet another object to provide a method and apparatus which can ensure the stabilization of electrical signals during reading and writing operations by installing an active element at a suspension of the hard disk drive to control axial bead displacement of a spindle motor.
It is still yet another object to provide an apparatus for improving access time of a hard disk drive by stabilizing an initial settlement of a head by using an active damper.
It is also an object to provide an apparatus which moves a head to a safety area of a disk during a reading and writing operation when an outside impact exceeds a specified margin, and then returns the head to its prior track position.
These and other objects can be accomplished according to the principles of the present invention by: sensing tensive and compressive states of a suspension attributable to increases and decreases in flying heights of a head, providing to an active damper a value indicative of a reverse tensive force necessary to return the head to a normal flying height when the head is determined to be higher than the normal flying height in the sensing step, and providing to the active damper a value indicative of a reverse compressive force necessary to return the head to the normal flying height when the head is determined to be lower than the normal flying height in the sensing step.
Accordingly, in the sensing step, the tensive or compressive state due to a bend in the suspension following the flying height increase or decrease is sensed by the active damper.
The values indicative of the reverse tensive or compressive forces are provided to the active damper as a control signal to enable the active damper to adjust to the tensive or compressive forces in order to maintain constant flying height.
Moreover, the hard disk drive of the present invention resists impacts by: sensing an outside impact of the hard disk, determining whether a value indicative of the sensed impact is less than a standard marginal impact value, transferring the head to a safety area on the disk where no data exists when the sensed impact value is greater than the standard marginal impact value, confirming a constant flying height of the head, and returning the head to the track position occupied prior to transfer after a constant flying height of the head is confirmed. Accordingly, the head can be replaced to the track position previously occupied after the flying height is confirmed as steady and constant.